1. Field of Invention
This invention relates to methods and apparatus for semiconductor wafer processing and manufacture of micro-circuit devices, and more particularly to methods and apparatus for positively identifying the processing status of a plurality of semiconductor wafers that are being processed using multi-wafer cassettes as a transport method.
2. Background and Description of Related Art
As is well known, in semiconductor wafer processing, a semiconductor wafer is treated in a number of processing steps to form a plurality of micro-circuit devices on the wafer. Typically, such processing includes successive steps of chemically treating the semiconductor wafer, applying a photosensitive coating to the substrate surface, imaging a circuit pattern onto the substrate coating at a plurality of locations on the substrate using lithography equipment or the like, treating the exposed coating and then repeating the foregoing steps to build up the micro-circuit devices. Such processing treatment further includes, for example, solder printing processing to form electrical connections on the respective micro-circuit devices formed on the substrate. In order to produce micro-circuit devices in volume, large scale production facilities process hundreds of wafers during such processing. Conventional semiconductor wafer processing systems electronically track the process status with computer system controllers and displays that provide the operator with limited status messages, for example, cassette A, wafer no. 15. However, in the event of a power outage, emergency power-off or system malfunction, the process status information may be lost or corrupted, so that when restarting the system, it is not readily possible to determine the processing state of the various wafers in a cassette, or full cassettes of wafers.
The methods and apparatus of the present invention overcome the problems of the prior art and improve the manufacture of micro-circuit devices by providing positive wafer process status identification during semiconductor wafer processing in which a robotic arm moves wafers between a storage cassette located on a cassette holding station and a wafer processing station. The system comprises a mechanical indicator flag movable between at least two, and preferably at least three, processing state indicating positions; and an actuator member connected to the indicator flag and actuated by movement of the robot arm to move the indicator flag. The robot is controlled to move the indicator flag to different processing state indicating positions via the actuator member during the processing according to the stage of the processing and the sensed position of the indicator flag.
The wafer process status identification system of the present invention provides a positive, i.e., fool-proof, indication of the processing state of each wafer cassette during the semiconductor wafer processing that allows an operator to immediately determine which cassette or cassettes are finished, which are partially processed and which are awaiting processing. Costs attributed to system status uncertainty during error recovery are reduced, and production efficiency is improved. These and other features and advantages of the invention are described in or are apparent from the following detailed description of the preferred embodiments.